There are known various antifouling paints which are based on metallic toxicants, mainly copper and tin compounds. Heavy metals of this type are undesired from an environmental point of view. According to the present invention there are provided antifouling paints which afford a very good protection of marine structure, and which are either free of heavy metal salts or which contain these in a substantially decreased quantity. Various phenyl-ethylsulfone compounds are known, but the main use of these is in insecticidal, acaricidal and fungicidal compositions of matter. Such compounds have not been used hitherto as active ingredients in antifouling paints for use with marine structures.